1. Field of the Invention
This invention is generally directed to acid etch solutions which are used in preparing the surface of teeth prior to the bonding of orthodontic brackets thereto and more specifically to either a solution or gel etch which contains minor amounts of phosphoric acid. The amount of phosphoric acid in the etch should not exceed approximately 5% by weight of the solution or gel compound and preferably should be within a range of approximately 0.51 to 1.02%. The acid etch of the present invention is specifically designed to prepare the tooth surface for the application of ceramic orthodontic brackets. The solution is specifically formulated to permit sufficient etching of a tooth surface so as to insure a strong and secure bond of the ceramic bracket to the tooth surface but which allows the bracket to be easily removed by the orthodontist without causing hard to the exterior enamel of the tooth and without the need to grind or use excessive force to remove the bracket from the tooth surface.
In other embodiments of the invention, the exact percent of phosphoric acid in solution or in the gel compound may vary slightly depending upon the configuration of the base of the ceramic bracket. It is invisioned that the bases of some ceramic brackets may be ribbed or otherwise configured so that the entire base of the bracket does not contact the tooth surfaces. In these instances, the percentage of phosphoric acid may be increased due to the decrease in surface area of the base portion of the bracket in contact with the tooth surface.
2. History of the Related Art
In preparing teeth for the application of orthodontic brackets, it is first necessary that the surface of the teeth be cleaned and then etched. Cleaning is accomplished by using a prophy brush with a flour-of-pumis and water solution after which the surface of the tooth is thoroughly rinsed and dried utilizing compressed air. Thereafter, the surface to which an orthodontic bracket is to be secured is etched with an acidic etching solution with the application of the etching solution being made utilizing small cotton processor pellets. The etching solution is applied for approximately 60 seconds after which the etching solution is rinsed thoroughly with water and the surface of the tooth again dried. The acid etch is applied to the tooth in order to slightly roughen the exterior surface enamel so as to promote an effective bonding of an after applied bonding agent or agents which will be utilized to secure the orthodontic bracket to the surface of the tooth.
In conventional acid etch solutions which incorporate phosphoric acid, the amount of phosphoric acid is normally present in a range between approximately 37 to 50% by weight in solution or in a gel compound. The use of such conventional phosphoric acid etches has proved to be reliable when applying metallic and plastic brackets. However, with the advent of the newer ceramic brackets, a great deal of problems have been encountered by orthodontist and, in particular, with respect to removing the ceramic brackets which have been applied to teeth which have been prepared utilizing conventional phosphoric acid etch solutions. More specifically, the bases of ceramic brackets are usually flat but may exhibit a microscopic or macroscopic honeycomb appearance and the bases may be coated with a silane coupling agent. In practice it has been found that it is often extremely difficult to remove ceramic brackets once they have been applied to the tooth surface. In many instances, surface tooth enamel has been removed concurrently with the removal of ceramic brackets and in some cases tooth fractures have occurred. This has required that, in some cases, ceramic brackets be filed from the surface of the tooth since the brackets cannot be removed by the application of simple pressure utilizing conventional orthodontic tools. The present situation has lead many orthodontist to suspend use of ceramic brackets in many instances.